Rotor end cap



Feb. 3, 1959 I NNNNNN OR Pia/2A- C. Rushing.

ATTORNEY uoron END CAP Frank C. Rushing, Pittsburgh, Pa., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application September 16, 1946, Serial No. 697,329

2 Claims. (Cl. 233-27) The present invention relates to high-speed centrifugal separators and more particularly to an end cap for the bowl of such separators.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, constructions, arrangements, combinations, and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of the invention.

Of the drawings:

Fig. 1 is a vertical cross-sectional view of a typical and illustrative embodiment of the end cap of the present invention.

Fig. 2 is a horizontal cross-sectional view taken along line 22 of Fig. 1; and,

Fig. 3 is a horizontal cross-sectional view taken along line 3-3 of Fig. 1. I

It is an object of the present invention to provide an improved end cap for the rotor or bowl of a high speed centrifugal separator. A further object is the provision of an end cap for the rotor or bowl of such a separator which is adapted to utilize the countercurrent flow principle in operation. Still another object is the provision of a centrifuge rotor or bowl cap which has an extremely efiicient seal with respect to the rotor or bowl wall. The invention further provides a centrifuge rotor or bowl cap permitting free and efficient countercurrent flow of gas therethrough and effecting a desired distribution of gas in the rotor or bowl. A further object is the provision of an end cap which aids heat transfer with respect to gas passing through the cap contributing to the efliciency of the separation process.

The end cap herein shown and described is particularly adapted for use on the bowl of a centrifugal separator adapted to rotate at speeds of the order of 30,000 revolutions per minute which may be used, for instance, in the separation of the various isotopes or compounds of the various isotopes of elements, the isotopes or compounds thereof preferably being in the gaseous form when processed in the centrifuge. The centrifuge mentioned is of the continuous countercurrent flow type, by which is meant a construction adapted to have a fluid mixture of heavier and lighter components flowed therethrough in oppositely directed streams. In the centrifuge bowl the radially outer portion of the material being processed is enriched in the heavier component and the radially inner portion of the material is enriched in the lighter component of the mixture. The material to be separated is continuously flowed into the bowl at each end thereof and continuously withdrawn from the bowl at each end thereof, and the ingoing and outgoing streams at either Fatented F oh. 3, 1959 end of the bowl are radially off set from each other in order to utilize the separative work of the bowl. In the centrifuge with which the end cap of the present invention is used the material enters in a single stream at each end of the bowl and is withdrawn in a single stream at each end of the bowl, and an end cap as herein shown is positioned in each end of the bowl to convey the streams to and from the bowl.

Referring now 'in detail to the illustrative embodiment of the invention shown by way of example in the accompanying drawings, the end cap is shown as positioned over the lower end of cylindrical rotor or bowl 10 of the centrifuge. The bowl is mounted for rotation by means of a hollow shaft 11 which supports the bowl through the end cap, and a second hollow shaft or tube 12 is concentrically arranged within shaft 11. There is thus provided a pair of passages 13 and 14, the former being the bore of tube 12 and the latter being the annular space between tubes 11 and 12, and these passages are adapted to carry the countercurrent flow of fluid to and from the bowl. The end cap comprises a central cap portion 15 having a central aperture to receive shaft 11, and the cap portion is held and sealed with respect to the shaft by means of a clamping flange 16 secured by tap bolts 17 to the cap portion. An aluminum gasket 18 is clamped between the flange, the cap portion, and the hollow shaft. The cap portion 15 is provided with a plurality of radial passages 19 leading to a central annular relieved portion of the cap portion which receives an annular disc 20. The disc is provided with. a plurality of radial passages 21 communicating with passages 19 and leading to the outer periphery of the disc, which is somewhat spaced from the bowl wall 10. Fluid communication is thus established between annular passage 14 through apertures 22 in shaft 11 with the inner surface of bowl wall 10 where the flow of the heavier component of the mixture takes place.

The central cap portion 15 is provided with a central, axially extending, externally threaded extension 25 which receives a cooperatingly threaded assembly nut 26. The assembly nut has a radially outer frusto-conical portion which engages the adjacent surface of disc 20 holding the latter in assembled position, and is provided with a plurality of radial passages 27 leading from a central space 28 to the periphery of the assembly nut. The assembly nut has a web portion 29 closing the space 28, and there is thus provided a fluid paassage between inner passage 13 in the shaft assembly and a position in the bowl intermediate the axis and periphery, where a flow of lighter components of the mixedfluid takes place.

The radially outer portion of the cap and bowl wall 10. The end of wall 10 is bored to a larger internal diameter to provide an interior shoulder, the surface of which preferably lies in a plane perpendicular to the axis of the bowl. The central cap portion 15 is provided with an integral expansion portion 32 of folded form, that is to say it appears in cross section as U- shaped. An integral flange 33 is provided on the exterior edge of the closure and a sealing surface 34 on the side of the closure interior to the flange. The sealing portion 34 is such that it will fit closely within the diameter of the bowl wall 10. The diameter of the flange 33 is such that it will fit closely into the bored out portion of the bowl and the flange will bear against the shoulder 30. it is preferred that this fit so tightly that it will require heating of the bowl and cooling of the end cap in order to permit one to slip into the other.

The sealing portion 34 is provided with a plurality of grooves 35 Which are deeply cut and extend completely around the portion opposite and facing the inner surface of the wall 10. In each groove 35 there is positioned an annular gasket 36 madepreferably of rubber or rubber-like material.

The rubber-like material, 36, seals because centrifugal force produces very high pressure against the wall of the bowl and against the projections from the end cap. The presence of this seal is not essential to successful operation, and it may be eliminated if desired.

The aluminum gasket, 30, consists of a small aluminum ring which initially sticks out above the end cap surface. When the end cap is pressed against the seat adjacent to the gasket, the gasket is plastically and elastically deformed. The plastic deformation allows the gasket to smear and seat against the surfaces. The elastic deformation maintains pressure against the seats. The end cap actually does not bottom against the gasket. This may be seen by reference to Fig. 1 of thedrawings.

When the bowl is not rotating an interference fit exists between the end cap and the bowl at the diameter 40 (Fig. 1).

At top speed the bowl expands more than the end cap, and the interference between the two parts at 40 is reduced practically to zero. If the assembly started Without an interference fit, there would be relative radial motion at the gasket and the seal would deteriorate. Also, if relative radial motion were allowed the end cap might shift its position in the bowl at top speed and produce unbalance.

he gooseneck 32 allows the end cap to expand a sufiicient distance to avoid relative motion at the joint. If the gooseneck were not used, a much greater initial interference fit would be necessary because a simple disk would not expand nearly as much as the present end cap seal. The gooseneck also allows the operation without excessive stresses in the end cap.

The end cap is held in place at its outer periphery by means of an annular nut 37 which has inter-engaging square screw threads with the interior of bowl wall 10. Nut 37 may be screwed into place by lugs 38, and a gasket 39 is placed between the nut and the flange 33. It will be understood that the seal is effected by the pressure of the gaskets 36 on the interior side of the bowl wall 10 and it will be apparent that the greater the centrifugal force, the greater will be the pressure between the gasket and bowl wall.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scopeof the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

I claim:

1. An end cap for a centrifuge bowl having a cylindrical wall mounted for rotation upon a hollow shaft having a plurality of separated passages therein, an annular cap member extendingradially between said shaft and said wall, an annular disc member seated in a recess in said cap member, the outer periphery of the disc being spaced from said wall, said annular cap and disc members having radial, intercommunicating passages communicating with one of said shaft passages, said cap member having an axially extending central threaded projection, and an assembly nut threadedly engaged on projection and abutting said disc member, said assembly nut having radial passages communicating with another of said shaft passages and opening into the bowl at a position between said shaft and bowl wall.

2. An end cap for a centrifuge bowl having a cylindrical wall mounted for rotation upon a hollow shaft having a plurality of separated passages therein, an annular cap member extending radially between said shaft and said wall, said member having an annular section of substantially V cross-section and an outer peripheral enlarged portion engaging said bowl wall, an annular disc member seated in a recess in the axially inner surface of said cap member, the outer periphery of the disc being spaced from said wall, said annular cap and disc members having radial, intercommunicating passages communicating with one of said shaft passages, said cap member having an axially extending central threaded projection, and an assembly nut threadedly engaged on said projection and abutting said disc member, said assembly nut having radial passages communicating with another of said shaft passages and opening into the bowl at a position between said shaft and bowl wall.

Beams: A Tubular Vacuum Type Centrifuge, Review of Scientific Instruments, vol. 9, pages 413, 416 (1938). 

